This invention pertains to particles comprised of certain polymers in combination with magnetic metals, to compositions including such particles, and to methods of making and using such particles and compositions. More particularly, this invention pertains to such particles in which the polymer has a biochemical function.
Biologically active magnetic particles may find use in a variety of preparative and diagnostic techniques. Among these is high gradient magnetic separation (HGMS) which uses a magnetic field to separate magnetic particles from suspension. In instances where these particles are attached to biological materials of interest (e.g. cells, drugs), the material of interest may thereby be separated from other materials not bound to magnetic particles.
Several properties are important if a magnetic particle is to be useful in biological and diagnostic systems. First, the particle must possess the necessary biological activity, affinity, or reactive nature, by which it will perform its function. Second, the particles must be suspendable in an aqueous medium for delivery to the biological or reaction system. It may also be desirable that the particle suspension be stable (i.e. not settle out or agglomerate). Finally, small particle size may be desirable so that a suspension of the magnetic particles may be filter sterilized by conventional techniques.
Many techniques have been suggested in the prior art for the preparation of magnetic particles or organomagnetic materials. U.S. Pat. No. 4,001,288 to Gable et al. discloses a preparation of magnetic organo-iron compounds which are both water soluble and strongly magnetic. In the preparation taught by Gable et al., ferrous iron in solution is treated with hydrogen peroxide and then with ammonium hydroxide in order to precipitate an iron oxide compound. This compound is subsequently oxidized with peroxide, treated with a hydroxy-carboxylic acid, and reacted with an alkaline material in order to form a soluble product.
Gable et al., also disclose the introduction of proteins or "protein degradation products" into the ferrous iron solution which is subsequently reacted to precipitate iron oxides. The only material for which examples are presented is the hydrolysis product of gelatin treated with hydrogen peroxide.
U.S. Pat. No. 4,452,773 to Molday discloses "colloidal sized" iron oxide particles coated with a polysaccharide, (exemplified in the patent by dextran and dextran derivatives). Although Molday's particles are prepared in a manner somewhat similar to that used in preparing particles in the present invention, they are believed to be substantially different from the particles of the present invention.
U.S. Pat. No. 4,454,234 to Czerlinski teaches the preparation (generally by suspension polymerization on a magnetic particle substrate) of coated magnetic particles which are reversibly suspendable in solution. The suspension parameters taught by Czerlinski involve the effect of the Curie temperature of his magnetic particles which may be used alternately to cause the particles to be magnetic and non-magnetic. When the particles are magnetic, they tend to agglomerate, but may be resuspended after heating the particles to a temperature above the Curie temperature of the magnetite contained therein.
U.S. Pat. No. 4,230,685 to Senyei, et al., discloses the preparation of microspheres containing magnetite, albumin, and protein A. The preparation taught by Senyei does not involve the precipitation of magnetite in the presence of these other constituents, but rather is a coating of preformed magnetite particles.
Other patents which may be considered to be of interest include U.S. Pat. Nos. 4,152,210 to Robinson, et al.; 4,335,094 to Mosbach; 4,018,886 to Giaever; and 4,070,246 to Kennedy, et al. While these patents all disclose the preparation or use of magnetic-biologic particles, none of these are thought to be similar to those of the present invention.